This invention relates to heating apparatus and more particularly to a furnace especially in a controlled atmosphere adapted for high speed, high volume continuous processing of workpieces.
An infrared furnace provided with an endless conveyor belt is highly useful since infrared heating elements located in different zones along the length of the heating chamber of the furnace can be quickly heated up as needed to give a desired temperature profile in the direction of travel of the conveyor belt.
In an infrared furnace, the level of the internal ambient temperature that can be attained within its heating chamber is limited by the maximum allowable temperature of the infrared source. This internal ambient temperature is determined by the temperature of the interior walls of the heating chamber and any objects enclosed therein which heat up by absorbing the radiation emitted by the infrared heating elements.
Prior art attempts to maintain the ambient temperature in the heating chamber of an infrared furnace at a safe level include providing for cooling the metal walls of the heating chamber; providing metal reflectors adjacent the metal walls of the heating chamber for reflecting the radiation from the infrared heating elements back onto the workpieces being carried on the moving conveyor belt; and providing for cooling each of the infrared heating elements by enclosing its envelope within a cooling tube which is transparent to the infrared radiation.